This invention relates to a stopper rod for controlling the flow of molten metal from a ladle or a tundish.
As is well known, stopper rods used in the casting of molten metals are connected, in use, by a metallic carrier rod to a lifting device which is arranged to move the stopper rod in the direction of its longitudinal axis so as to control flow of molten material through an outlet in the vessel in which the stopper rod is received. It is also well known to provide the carrier rod with a gas channel for introducing inert gas into the stopper rod. The extreme conditions under which the stopper rod operates in use make it difficult to ensure that the stopper rod is always securely connected to the carrier rod when the temperature increases, and to ensure that there is gas tightness so that there is no significant loss of inert gas and no penetration of atmospheric air into the stopper rod, the latter causing oxidation of the molten metal and lowering the quality of the final product.
DE4444617A1 and EP1140393 both address the above mentioned problems, amongst others, and each discloses the use of a cylindrical insert or sleeve disposed around the carrier rod to compensate for the effect of expansion of the carrier rod.